# Polar and Ferrel cells

Extremely cold, dense air also subsides over the North and South Poles. It produces the two polar high-pressure regions. Air flows out from them and is deflected to become the polar easterly winds.

### The Coriolis effect

Any object moving toward or away from the equator and not firmly attached to the surface does not travel in a straight line. As the diagram illustrates. It is deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Moving air and water tend to follow a clockwise path in the Northern Hemisphere and a counterclockwise path in the Southern Hemisphere.

The French physicist Gaspard Gustave de Coriolis (1792-1843) discovered the reason for this in 1835, and it is called the Coriolis effect. It happens because the Earth is a rotating sphere, and as an object moves above the surface, the Earth below is also moving. The effect used to be called the Coriolis "force," and it is still abbreviated as CorF, but it is not a force. It simply results from the fact that we observe motion in relation to fixed points on the surface.

The Earth makes one complete turn on its axis every 24 hours. This means every point on the surface is constantly moving and returns to its original position (relative to the Sun) every 24 hours, but because the Earth is a sphere, different points on the surface travel different distances to do so. If you find it difficult to imagine that New York and Bogotá—or any other two places in different latitudes—are moving through space at different speeds, consider what would happen if this were not so: the world would tear itself apart.

Consider two points on the surface, one at the equator and the other at 40° N, which is the approximate latitude of New York and Madrid. The equator, latitude 0°, is about 24,881 miles (40,033

km) long. That is how far a point on the equator must travel in 24 hours, which means it moves at about 1,037 MPH (1,668 km/h). At 40° N, the circumference parallel to the equator is about 19,057 miles (30,663 km). The point there has less distance to travel and so it moves at about 794 MPH (1,277 km/h).

Suppose you planned to fly an aircraft to New York from the point on the equator due south of New York (and could ignore the winds). If you headed due north, you would not reach New York. At the equator you are already traveling eastward at 1,037 MPH (1,668 km/h). As you fly north, the surface beneath you is also traveling east, but at a slower speed the farther you travel. If the journey from 0° to 40° N took you six hours, in that time you would also move about 6,000 miles (9,654 km) to the east, relative to the position of the surface beneath you, but the surface itself would also move, at New York by about 4,700 miles (7,562 km). Consequently, you would end not at New York, but (6,000 - 4,700 =) 1,300 miles (2,092 km) to the east of New York, way out over the Atlantic, somewhere due south of Greenland.

The size of the Coriolis effect is directly proportional to the speed at which the body moves and the sine of its latitude. The effect on a body moving at 100 MPH (160 km/h) is 10 times greater than that on one moving at 10 MPH (16 km/h). Sin 0° = 0 (the equator) and sin 90° = 1 (the poles), so the Corio-lis effect is greatest at the poles and zero at the equator.

The polar easterlies and mid-latitude westerlies meet along the boundary between polar and tropical air. This is known as the polar front. At the top of the polar front, close to the tropopause, the temperature difference on either side is very large. It produces the polar front jet stream, which is a strong, high-level wind blowing from west to east in both hemispheres.

Air rises along the polar front. Some of the air flows back toward the pole, where it cools and subsides once more. This produces a second set of cells, called the polar cells.

Three-cell model. The tropical (Hadley) and polar cells are directly driven by convection. The middle-latitude (Ferrel) cell is indirect, because it is driven by the polar and tropical cells.

Some of the air flows toward the equator. Over the Tropics it meets the high-level air of the Hadley cells and subsides with it. This forms a third set of cells. Their existence was discovered by the American meteorologist William Ferrel (1817-91) and they are known as Ferrel cells.

There is another region of light surface winds, known as the horse latitudes, where the subsiding air reaches the surface and divides. Historically, ships often carried cargoes of horses. If the ships were becalmed, supplies of drinking water sometimes ran short. Horses often died of thirst when this happened, and their bodies were thrown overboard, hence the name.

The Hadley cells and polar cells are direct cells, driven by convection and the subsidence of cold, dense air. The Ferrel cells are indirect cells, driven by the direct cells to the north and south of them. Together, the Hadley, Ferrel, and polar cells comprise the three-cell model shown in the diagram.

Between them, these cells transport warm air away from the equator and cool air toward the equator. Without them, tropical temperatures would be much higher than they are and polar temperatures much lower.

Three-cell model. The tropical (Hadley) and polar cells are directly driven by convection. The middle-latitude (Ferrel) cell is indirect, because it is driven by the polar and tropical cells.

Continue reading here: Transport Of Heat By The Oceans

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### Responses

• harley
What are polar cells (ecology)?
3 months ago
• Edward
Why do polar cells form?
3 months ago
• Pearl
Is the UK between the ferralk and polar cells?
1 year ago
• Rudigar
Does the polar cell move clock wise?
1 year ago
• eemil
What drives ferrel cells?
2 years ago
• ashley
How is a ferrel cell genereated?
2 years ago
• Rufus
What happens to the temperature when some air escapes from the cells ferrel polar an hadley?
2 years ago
• raymond
What direction does a polar cell move in?
2 years ago
• Matilda
How the polar cell effects the temperature?
2 years ago
• ruben
What would happen if the polar cell heats up?
2 years ago
• gabriele
What happens when the polar cerrel cells meet?
2 years ago
• stephan
What kind of weather is in the polar cell?
2 years ago
• LINDA SMALLBURROW
How high does the ferrel cell go?
2 years ago
• Costantino Romano
What type of climate would you expect to find between a ferrel cell and a polar cell?
2 years ago
• mhret
What path does a polar cell take?
2 years ago
• Theo
What happens in the polar cel for the coriolis effect?
2 years ago
• aziz amanuel
How do polar cells influence?
2 years ago
• Sarah
How polar cell affects global warming?
2 years ago
• lydia
What are polar cell on world?
2 years ago
• luigina
What weather do you get at the feral and polar cells?
2 years ago
• Kerttu
What is the climate supposed to be like in the Ferrel cell?
2 years ago
• j bachmeier
What are the effects of the hadley polar ferrel cells on austrlia?
2 years ago
• mari nyk
What are polar cells in enviormental science?
2 years ago
• GERDA
Why is the clmate wet between the ferrel and ploar cells?
2 years ago
• Tewolde
What is the impact of polar, hadley and ferrel cells on the worlds climate?
2 years ago
• Elisa Santala
How are cells affected by global warming?
3 years ago
• vihtori
What is the climate like in the polar cell?
3 years ago
• Emilie
What cuases the hadlet, ferrel and polar cell to be weaker?
3 years ago
• REN
Why is the climate wet where polar and ferrel cells meet?
3 years ago
• gorbulas
How do the hadley and ferrel cells relate?
3 years ago
• arvi
How are polar deserets afftected by the polar cell?
3 years ago
How are convection currents related to ferrel hadley polar cells?
3 years ago
• Leah Trommler
What is the effect of the polar cell?
3 years ago
• abby
What happened in the polar cell?
3 years ago
• kayden
Is a ferell convection cell in a tropical region?
3 years ago
• Sophie Fiedler
How does the ferrel cell affect the climate?
3 years ago
• maci
How the ferrell cells affect climate?
3 years ago
• quinn clark
How have the polar, ferrel and hadley cells changed?
4 years ago
• jordan maclean
What is the impact of polar cell in the environment?
4 years ago
• JOHAN
Are the polar and Ferrell cells changing?
4 years ago
• tiffany
What is the weather in the ferrel cell like?
4 years ago
• safa
What separates polar cell from ferrel cell?
5 years ago
• Fausto
Is the jet stream the top of the Hadley / Ferrel / Polar Cells ?
5 years ago
• bruno
What is hadley cell ferrel cell and polar cell in environment physcst?
5 years ago
• may
What is the ferrel cell driven by?
10 years ago
• ASMARA
What is the polar cell driven by?
10 years ago
• mario
Where does the sun set in the middle latitudes of the Northern Hemisphere on June, 22?
10 years ago